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[HP48GX] Testing repaired keyboard
08-01-2016, 03:49 PM
Post: #12
RE: [HP48GX] Testing repaired keyboard
Hi fnas,

The sort of material you are looking for is a stiff but compressible foam rubber. One suggested source is a thin mouse pad. You'll see it has the right consistency to match the rubber strip you are replacing. By sheer luck, the anti-static pad I have on my work surface is just the right thickness to match the height of the rubber strip. The pad now has a number of rectangular notches along the bottom Smile

You will need to take some care in removing the old strip, as it is glued to the case and will tear easily if mishandled. The approach I have used is to take the thin blade of an Xacto knife and insert it between the top of the strip and the plastic case, then press down to pull the strip away from the case and break the glue seal. Do the same again by placing the blade along the bottom of the strip and press upward. If you repeat this once or twice, you will loosen enough of the seal so that you can peel the strip from the case without tearing it or leaving small bits if it behind.

Have a look at the article "Calculator Restorations" by Geoff Quickfall in the #19 issue of HP Solve for some excellent guidance. You can find the issue here:

When you replace the CPU board, press down on it before closing the twist ties so you get a good contact between the keyboard flex circuit and the PCB, and the same between the LCD zebra stripes and PCB. The twist should return to a 45 degree angle or better. Use your multimeter to verify continuity between the metal case the the PCB pad that the twist should touch.

Good luck!
~ Mark

Remember kids, "In a democracy, you get the government you deserve."
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[HP48GX] Testing repaired keyboard - fnas - 07-21-2016, 09:29 AM
RE: [HP48GX] Testing repaired keyboard - mfleming - 08-01-2016 03:49 PM

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